Abstract
Keywords: Judder, Drone, Thermo-elastic, Instability, Brakes
Disc Brake judder is one of the major concerns for brakes on high performance vehicles because of the energy being absorbed and dissipated by the brakes. If the brake absorbs energy significantly faster than it can dissipate it then the disc experiences high temperatures and as such thermal deformation. This deformation may be recoverable and as such judder may be temporary. The issue becomes more serious if the deformation does not recover and so the disc will hold a permanent wavelike shape resulting in classical judder. For the brake to more readily discharge the heat vented discs are employed but the overall purpose and effect is sometimes confused. Vented discs bring with them another form of thermal deformation in the form of "hot spotting" or "blue spotting". Such deformation is localised about the disc but the overall effect is a droning sound resulting from high frequency judder - caused by localised thermal deformation both across and around the disc surface. It is tentatively believed that high frequency judder (drone) is caused by uneven temperature distribution on the disc surface, or within the brake rotor, causing both thermo elastic deformation and thermo elastic instabilities. This paper focuses on establishing a disc design that avoids heat "sinks" and moves towards a more even heating and cooling of the disc surface and body. Such a design considers the geometry of the disc/pad interface and on the rib profiling. The purpose is not necessarily to increase the cooling capacity of the brake disc but to encourage a more temperature stable brake disc by means of adequate consideration of the heat distribution across, around and through the disc in addition to overall cooling of the disc body. The paper is aimed at detailing the preliminary vehicle testing which has been performed which will allow for accurate validation of dynamometer testing and computational analysis. Promising results have been obtained and are presented and discussed. Conclusions have been drawn with recommendations for further work.